1. Field of the Invention
The present invention relates to control of a motor, and particularly relates to a motor driver that drives a stepping motor.
2. Description of the Related Art
A stepping motor is used in order to operate sheet feed units of a copier and a printer or a capture unit of a scanner. The stepping motor includes a plurality of coils and a rotor. In the stepping motor, the rotor is pulled by magnetization force generated in such a manner that these coils are magnetized every time when a pulse signal is applied thereto from outside, and the rotor rotates by step by step. In general, a drive current for driving the stepping motor is adjusted by a motor driver, and rotation of the stepping motor is controlled.
For the purpose of reducing damped oscillations of the stepping motor, for example, a method is proposed, in which the drive current is decreased to reduce the oscillations in a low-speed rotation range and at the time of stopping the rotor.
However, in order to realize the optimum control states individually for a variety of stepping motors, it is necessary to set rates of attenuating the drive currents (hereinafter, referred to as “decay rates”) in response to magnetization methods, drive current values and the like of the stepping motors. Therefore, the motor driver is required to have a function to make it possible to set in detail the decay rate of the drive current in response to specifications, usage purpose and the like of each of the stepping motors.